This invention is related to data storage and retrieval device which utilizes magnetic disk, magneto optical disk, optical disk, and magnetic tape etc. Especially this invention is related to data storage and retrieval control method in which inter sector gap area is reduced while data recording and reproducing, and also related to device using it.
Data recording and reproducing method of conventional data storage and retrieval device is disclosed with an example of magnetic disk device. However the present invention is effective not only in magnetic disk device but also various data storage and retrieval devices in which a train of data is separated to one or more blocks and recorded to the data recording medium with arranging a gap before or after each sector, and data reproducing is performed through a reproducing head which faces and moves against said recording medium.
In a magnetic disk device, concentrically shaped recording area called track is arranged on a magnetic disk namely the recording medium, and data recording and reproducing is performed by the information on the track. Servo area is arranged intermittently and periodically on this track, and data area is also arranged between the servo area. Said data recording area usually consists of plural of data sectors. Between the sectors, there are gap area which compensates the rotational speed deviation or delay time of the operation of electronic circuit. Accordingly data cannot be recorded here.
Each sector consists of ID portion and data portion. ID portion consists of synchronizing pattern to distinguish data while data reproducing, ID information to identify the data sector, and error check codes to detect the ID information error. Data portion consists of synchronizing pattern to distinguish data while data reproducing, data information, and error correction code (ECC) etc.
Recording and reproducing circuit which performs recording and reproducing of data on said data portion consists of read circuit, write circuit, and data control circuit. Read circuit handles reproducing of signal from ID portion and data portion. Write circuit handles recording the signal to data portion. Based on the servo sector signal of said servo area, data control circuit generates data sector signal which is activated at the start point of synchronizing pattern of ID portion, and controls overall recording and reproducing operation of the device.
A data recording procedure is as follows: ID data is reproduced with reference to the data sector signal as the origin, it is confirmed that the reproduced ID data identifies the correct sector to be recorded, and write data is recorded by the write circuit. A data reproducing procedure is as follows: ID data is reproduced, it is confirmed that the reproduced ID data identifies the correct sector to be reproduced, the following data area is read back by the read circuit, and the desired data of the sector is obtained.
Further, detail procedure is described as follows. Read gate signal is activated by the data control circuit at the appropriate timing during the synchronizing pattern area of the ID portion with referring to the data sector signal as the origin. Read circuit synchronizes with the signal recorded in ID portion, decodes the reproduced signal to data, gets the ID information, and transmits the ID data to data control part. Data control circuit verifies the error check code of ID information and temporarily closes the read gate, then reactivates the read gate signal at an appropriate timing during the synchronizing pattern of the data portion after ID portion. Read circuit synchronizes with data portion, decodes the reproduced signal, and transmits the reproduces data to data control circuit. After decoding error correction code portion (ECC) of data portion, data control circuit closes the read gate, and shifts to a status of waiting the data sector signal for decoding next ID portion.
In a series of data recording and reproducing operation, gap areas are arranged between data sectors, or before and after ID portion and data portion, in order to compensate the deviation of recording position which is caused from the rotational speed deviation of magnetic disk which is the recording medium in magnetic disk device, or the deviation of tape running speed in magnetic tape drive, and to compensate the delay in data recording operation of write circuit, or the delay in data reproducing operation of read circuit.
In most cases, the rotation of magnetic disk is controlled based on a clock signal generated by a crystal oscillator, so that usually the rotational speed is stable. However when the device is exposed to a shock or vibration, or when seek operation occurs, the rotational speed of the disk varies because of the deviation of the power voltage or mechanical resonance from seek operation. In such cases the amount of the deviation of the rotational speed is about 0.1%. Above mentioned gap areas were necessary to avoid the data destruction from the deviation of the rotational speed.
Delay time in operation of write or read circuit varies according to the data conversion method (coding format ) or the reproducing method of reproducing the data recorded on the data storage medium (here magnetic disk). As for the coding method, recently more efficient block coding method such as 8 to 9 coding method or 16 to 17 coding method is generally used instead of formerly used 2 to 7 RLL or 1 to 7 RLL. As for the reproducing method, PRML method (Partial Response Maximum-Likelihood) or EPRML (Extended Partial Response Maximum-Likelihood) is generally used in order to obtain the better signal to noise ratio. With the increasing complexity of the data conversion method or signal reproducing method, coding or decoding time increases, accordingly the operation time (delay time in data recording or reproducing) required the reproduced data to reach to data control circuit from read circuit increases. Now data control circuit cannot start the operation of next data portion or ID portion until ECC decoding operation of the reproduced data finishes. So gap area to wait the delay time of write or read circuit was necessary before and after the data portion or ID portion.
Track format in the conventional magnetic disk device is shown in FIG. 7. Recording and reproducing operation of data is performed depending on one data sector signal (for write and read) as timing signal. Servo area and SYNC pattern, those are necessary to record and reproduce data on data area, data recording area, gap area to compensate rotational speed deviation, and gap area to compensate the operation time (data conversion delay time) of write or read circuit are intermixedly arranged on the track. And there are time delay each between write data to be recorded on the recording medium, actually recorded data on the medium, and reproduced data respectively.
A method to delay the output of index signal and sector signal except formatting in order to avoid write splicing is disclosed in unexamined patent publication 5-303836 Japan. However only the timing of generating the sector signal is changed between formatting and not formatting, but there is no effect to reduce above mentioned gap area (namely the area cannot be used to store data).
In a magnetic disk device by the prior technology, starting of write or read operation of data is triggered by the data sector signal generated from servo signal. The data sector signal was generated at the same timing for both writing and reading data. In such above mentioned prior control method of data recording and reproducing, said gap area is determined by the total of the deviation of relative speed (rotational) of the medium, the delay in write operation, and the delay in read operation. Originally the gap area cannot be used for data recording. Accordingly by increasing the gap area, the actual data recording area decreases.
The purpose of the present invention is to eliminate the portion of gap area which is useless to store the data, so that to increase the substantial data recording area of the recording medium. Another purpose of the present invention is to reduce the portion of gap area with which the delay time of read or write operation is compensated, so that the efficiency of the data recording is improved.
In the data recording and reproducing method by the present invention, to achieve the above mentioned object, data sector signal generating means is provided where the timing of generating the data sector signal of data recording and reproducing is different. Here data sector signal is generated for each sector. Said data sector signal generating method can issue the two kinds of data sector signal either by changing the timing from one source signal or from pre-arranged two source signal of the different timing.
Further, in order to reduce the gap portion which compensates the delay time of read operation, it is provided with data sector generating means which generates data sector signal to start the data reading of the next sector before completing the data output operation of the current sector, and data reproducing means.
Or, it may be provided with data sector generating means which starts synchronizing with sync pattern and reproducing, before completing the data output operation of the current sector, and data reproducing means.
In order to reduce the gap portion which compensates the delay time of write operation, it is provided with data sector generating means which generates data sector signal to start the data writing for the next sector before completing the data output of current sector. Consequently, the gap area is substantially eliminated, and the data recording efficiency on the recording medium can be improved.